SECTION .text
global start

start:
mov rax, 0x2000004      ; syscall 4: write (
mov rdi, 1              ;    fd,
mov rsi, Msg            ;    buffer,
mov rdx, Len            ;    size
syscall                 ; )

mov rax , 0x2000001      ; syscall 1: exit (
mov rdi, 0              ;    retcode
syscall                 ; )

SECTION .data
Msg db `Hello, world!\n`
Len: equ $-Msg